The overall profitability of the smartphone market hit its apex in 2012, according to a prominent equity analyst.

Mobile expert Peter Misek says that market saturation and a lack of differentiation among high-end smartphones could put downward pressure on prices for the next iPhone, be it the iPhone 5S, iPhone 6 or something else.

In a research note released today, the Jefferies equity analyst writes that the iPhone is currently available to about two-thirds of mobile subscribers worldwide, and looking to grow that number further.

"This summer we believe Apple will add China Mobile (710M total subs; 88M 3G subs) and NTT DoCoMo (62M subs). While this raises Apple's served market to 76%, we note that 88% of China Mobile's subs are still on 2G," he says.

What's more, Misek implies that Apple's meticulously groomed brand image may be starting to show its age. He says a Jefferies survey recently found that the company's customer satisfaction rating was identical to that of rival Samsung.

The much-rumored cheaper iPhone would have to be cheap indeed to become the kind of hit Apple is hoping for, Misek says. Consumer budgets in the developing countries where he expects smartphone growth to take off are far smaller than those in developed nations, and competition from mid- and low-end rivals like Huawei, ZTE, Coolpad and Xiaomi will be fierce in China and India.

Overall, he says, iPhone profitability should be down in the 2013 calendar year, which makes 2012 the peak of Apple's earnings from that device. While a rebound is likely in 2014, Misek asserts that it won't reach 2012's level.

"As the most profitable smartphone OEM we also believe this means that global smartphone profits likely have peaked," Misek adds.